This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Herbs or undershrubs with bipartite hairs. Leaves entire or toothed. This genus differs very slightly from the last, distinguished by having a more flattened pod, wingless seeds, and a capitate or bilobed stigma. There are about a dozen species, chiefly from the Mediterranean, and extending to the Himalayas and North America. Name from the hand, and a flower; application uncertain. 1. Ch. Cheiri (fig. 33). Wallflower. - This needs neither description nor recommendation. The varieties it has given birth to are innumerable. Yellow, orange, purple, brown, and variegated single and double flowers occur. The Rocket Wallflowers form a distinct race, with long narrow flower-spikes. Though probably not indigenous, it is now found in many parts of Britain. The figure is more characteristic of the wild than the cultivated form.
2. Ch. Marshallii, syn. Erysimum. - A dwarf shrubby plant with evergreen leaves and a profusion of large fragrant orange-coloured flowers. It continues in flower from April till July. Supposed to be of hybrid origin, between the common Wallflower and Ch. alpinus.
3. Ch. alplnus. - A dwarf species about 6 inches high, with remotely toothed leaves and an abundance of pale yellow flowers. Summer. Mountains of Europe.
Fig. 33. Cheiranthus Cheiri. (1/4 nat. size.)